1. Technical Field
The invention relates to forming cup-shaped cylindrical members such as container bodies, from a blank of metal, and in particular to forming such bodies in a press which increases the roundness of the cylindrical-shaped sidewall of the body by reducing distortion thereof after the formed body passes through a cup drop sleeve by providing the cup drop sleeve with an internal diameter just slightly greater than the outer diameter of the cylindrical sidewall of the cup body formed by the die opening of the blank and draw die to reduce the spring back of the just formed cylindrical cup body.
2. Background Information
It is well known in the container forming art to form two-piece containers, that is, containers in which the sidewall and bottom wall of the container bodies are one-piece members and the top or end closure is a separate piece, by stamping disc-shaped blanks from a strip of sheet metal and then subsequently drawing the blank disc into a cylindrical cup-shaped body. In many can body forming presses, a generally cylindrical-shaped first stage body is ejected through a cylindrical cup drop sleeve by downward movement of a draw horn in combination with pressurized air, afterwhich the formed body is deposited on a pallet or a conveyor for subsequent forming or reforming to provide the final shape and size of can body.
It is desirable that the first stage cup-shaped body be as uniform in its roundness or cylindrical configuration as possible after ejection from a first stage press to provide for a more uniform can body prior to being fed into a subsequent reforming press. However, the flat blank disc when formed into a first stage cylindrical cup-shaped body by a blank and draw die and draw horn has the natural tendency or elasticity to spring back toward its original shape and distort into a somewhat oval shape due to the natural elasticity of the metal, which just prior to being formed into the generally cylindrical-shaped member, was a flat sheet. Heretofore, the cup drop sleeve of a press had an internal diameter relatively larger than the outer diameter of the just drawn cylindrical cup-shaped body to permit the first stage body to move freely therethrough, usually by pressurized ejection air which is emitted from openings in the draw horn.
The above forming and ejection operations occur in fractions of a second from the time the flat metal sheet is cut into a blank disc and then drawn into the first stage cup-shaped body which prevents the metal from setting sufficiently in its newly formed cylindrical shape to eliminate the spring back and distortion of the metal as it is ejected from the cup drop sleeve.
Therefore, it is desirable to develop an improved method and apparatus which reduces the distortion and spring back of a just formed cylindrical first stage cup-shaped metal blank upon being ejected from a first stage press without effecting the output speed, quantity and operation of the forming press.